Wood-pulp material



Nov. 18, 1930. J. H WALLACE 1,781,712

WOOD PULP MATERIAL Filed Feb. 5. 1925 d I J ,2 I PM I I 1: iwjgl Jul 5 II pm"--- INVENTOR Jase 1b fl. Wallace Patented Nov. 18, 1930 UNITED. sures PATENT OFFICE JOSEPH H. WALLACE, OP" STAMFORD, CONNECTICUT, ASSIGNOR TO PINE, WASTE PRODUCTS, INC., NEW YORK, N. Y.', A CORPORATION OF DELAWARE I WOOD-PULP MATERIAL Application filed February This invention relates to the material used for the manufacture of paper pulp, and has for its object the provision of a material which may be digested uniformly and efliciently.

The manufacture of paper pulp from wood 4 by chemical processes Involves what may be called'a fractional or selective attack upon the wood components; the object being to produce a disintegration or solution of certain relatively'less resistant components while leaving unattacked or unacted on certain relatively resistant components or cellulose. The yield and quality of product depend largely upon the care with which the operation is performed; upon the observance of conditions which have been empirically established by long practice. The greater the exactitude with which these conditions can be observed, the better the results; but, for various reasons, the ordinary practice is not standardized to the degree which is desirable. It is an object of the presentinvention to promote accuracy and umformity of operation by the provision of a standardized raw material; thereby facilitating standardization of the whole operation. With a standardized raw material there is no difiiculty in using solutions of exact and standard composition; or of employing exact temperatures and an exact time of digestion.

The moisture content of. wood, even from trees of one kind, varies greatly, from 20% or less in air dried or seasoned wood, to as much as 60% of the total weight of the wood, and this may amount to-as much as eight hundred gallons of water carried in one thousand cubic feet of chips. 7 Moreover the uneven distribution of the saps and soluble gums in the wood interferes materially with the desired uniformity'of digestion.

In the soda or sulfate processes, chipped wood in fragments long enough to give the desired'length of fiber in the pulp, is heated in'a digester with analkaline liquid to dis integrate and dissolve the non-cellulose portions, or lignin, so that they may be removed. A less concentrated solution is required for such chips as have a low moisture content and but a smallamount of saps and 5, 1925. Serial No. 6,958

terially affected or some portions of an individual chip become digested before therest of it. Spec of digestion is proportional to the strength of the alkaline liquid in contact with the fiber, and where a wet spot occurs or where there is an excess of sap or of soluble gums, the digesting liquid does not soak in readily and fora time is diluted. This time is that required for the equalization of the alkali content by diffusion, which is rela tively slow. This results in a large perpentage of screenings or rejects, which are a ossf,

In my Patent No. 1,560,448,,issued November 3, 1925, I have pointed out the desirability of having the moisture content of the woodchips as well as their resinous content uniform, and have shown that when it is uniformand known, the alkaline liquor may be always of the same; strength, and that the time required for treatment will be a redetermined known element. Inthe a oresaid'application, the process described was that applied to coniferous woods, and the moisture content was made uniform jby evenly distributing the resinous content thereof, or in partiall extracting the resinous content and eve y distributing the remainder. I have found, however, that the uniformity of moisture content and the even distribution of saps and soluble gums is of the utmostimportance in pulping all kinds of woods, even thosi containing no resin. Consequently this application in which is about its axis.

Fig. 1 of the drawing is a more .or less diagrammatic representation in longitudinal section of a drier mechanism of well known tate the chips as they pass through the drier.

1 These blades may be spirally disposed so as to assist in moving the chips through the drier longitudinally.- I

Within this rotary cylinder and extending through the center thereof is a pipe or flue 12 which serves to conduct heated air or waste gases into the drier and which provides a hot surface over which the contents of the drier fall as the outer cylinder rotates. The ends 13 and 14 of this application are stationary and suitable seals 13A and 14A are provided between them and the cylinder 10.

The source of heat, as shown for illustrative purposes, is from the waste gases of a steam'boiler 15, which after they have passed over a fuel economizer 16 are led by a flue 17 to the flue 12. They emerge into the end 14 of the drier and pass back throu h cylinder 10 into the-end 13 from which t ey are led by a flue 18. A fan or blower 19 is shown to assist the flow of the gases, the direction of movement'of which is indicated by ar-' rows.

Pro erly sized chips are introduced into 5 13 through a chute 20 and after passing through the drier they emerge through a chute 21 into-a receiving bin 27. Baiiie wheels 22 and 23 are shown in the chutes 20 and21 respectively."

24 designates asteam pipe, centrolled by" a valve 25.,- This pipe leads through the flue 12 and terminates in nozzles 26 in the space between the flue 12 and the cyliner 10.

If'desired, the chips may be subjected to saturated steam before they are carried to the drier. In fact such treatment alone would come within the sco e of this invention, as it would reduce t e moisture content of t e more heavily loaded chi s, especially such, if .there be any in w ich the moisture is frozen, and woul (1 increase the moisture'conte ntof the driest chips and thereby equalize to a substan ialfldegree the moisture content of the chigs as a whole. This also results in the desired diffusion of the saps and soluble gums. Preliminary steam treatment furthermore, raises the temperature of the chips and thereby puts them in better condition for cooking, as will be shown later;

The chips enter the drier at the end thereof where the hot ases are moisture laden and the effect of t e hot dam-p gases upon the driest of the chips is to increase their 'of the saps and soluble ums obtained. In

the cold season in nort ern climates, the

-moisture content of the chips is generally frozen. Naturally, the release of moisture from frozen chips which contain an excess of moisture is especially great when they are exposed to heat. Saturated steam ma be admitted through the nozzles 26 if desired, to insure definite relative humidity gondit ions in the atmosphere within the men As the chips' travel through the drier, more and more of their moisture content is removed and they are delivered into the bin 27 with their moisture content substantially uniform, their average moisture content reduced, and with their saps and soluble gums diffused.

. The degree of reduction can be carried to any desired extent b choosing the rateof movement of the ch1ps through the drier, the temperature of the hot gases and the length of the drier. If still greater reduction of moisture content is desired, the chi s may be carried through one or more 'ad 'tional driers. This, however, is not necessa as the even distribution and uniformity o the moisture content in the mass of chips is of greater importance than is the degree thereof. Moreover, if the chips are notto be digested immediately aftertheir conditioning, it is desirable to leave in them enough moisture to make them non-hygroscopic so that yea their distributed moisture content is stabiconditioned chips can be run directly into the digester hot, or where they may be stored in bulk in heated condition to await the next digester charge. This is a material gain as the pulp manufacturer sustains a loss in using wood of high moisture content by reason of a steam saving can the amount of steam required to raise the moisture. content to the temperature of digestion, and this is especially great when the moisture content is frozen, as it is invariably in the northern climates in the winter time. The additional heat thus required may amount to as much as one hundred pounds of coalper' ton of pulp; which in many mills is a burden amounting to 6% of the fuel requlrements for the entire pulp making process.

The chips treated in accorda nce with this invention are in'condition quickly to absorb into their cells the cooking li uors, the concentration of which can be pr etermined accurately. The time required for cooking is no longer empirical, and the difliculty of overcoo 'ng and destroying some of the chips before some of them or parts of some of them are sufficiently digested to be useful, is ob viated. Thus a greater amount of pulp is obtained from a given amount of material,

its quality is improved and uniform and satisfactory results may be relied upon. What I claim is: 1. The herein described method of making pulp which comprises removing excess moisture from a mass of wood chips by treating the mass with steam in the presence of heated gases and then at once transferring said mass tova digester.

2. The herein described method of making pulp which comprises reducing and unifying the moisture content of a mass of wood chips by treating the mass with steam in the presence of heated gases and then at once transferring said mass to a digester.

3. The hereindescribed method ofpreparin wood chips for pulp makin which comprises treating a mass of chips 0 unlike moisture content with steam in the presence of heated gases to reduce and unify their moisture content. a

4. The hereindescribed method of preparing wood-chips for pulp making which comprises difiusing the saps and soluble gums with steam in the presence of heated gases. 5. The hereindescribed method of preparing wood chips for pulp making, which comprises difiuslng the saps and soluble gums 1 simultaneously reducing and unifying the moisture content in said mass, and then introducing said mass into a suitable digesting liquor while it retains heat.

In witness whereof, I have hereunto set my hand this 2nd da of February, 1925.

J SEPH H. WALLACE. 

